Browsing by Author "Osborn, JC"

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    On line neutron flux mapping in fuel coolant channels of a research reactor
    (IEEE, 2014-01-30) Barbot, L; Domergue, C; Villard, JF; Destouches, C; Braoudakis, G; Wassink, D; Sinclair, B; Osborn, JC; Wu, H; Blandin, C; Thévenin, M; Corre, G; Normand, S
    This work deals with the on-line neutron flux mapping of the OPAL research reactor. A specific irradiation device has been set up to investigate fuel coolant channels using subminiature fission chambers to get thermal neutron flux profiles. Experimental results are compared to first neutronic calculations and show good agreement (C/E ~0.97). © 2022 IEEE
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    OPAL Reactor: calculation/experiment comparison of neutron flue mapping in fuel coolant channels
    (International Group On Research Reactors, 2013-10-13) Barbot, L; Domergue, C; Villard, JF; Destouches, C; Braoudakis, G; Wassink, D; Sinclair, B; Osborn, JC; Wu, H
    The measurement and calculation of the neutron flux mapping of the OPAL research reactor are presented. Following an investigation of fuel coolant channels using sub-miniature fission chambers to measure thermal neutron flux profiles, neutronic calculations were performed. Comparison between calculation and measurement shows very good agreement. © The Authors
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    Radiation shielding design for neutron diffractometers assisted by Monte Carlo methods
    (Elsevier B. V., 2006-11-15) Osborn, JC; Ersez, T; Braoudakis, G
    Monte Carlo simulations may be used to model radiation shielding for neutron diffractometers. The use of the MCNP computer program to assess shielding for a diffractometer is discussed. A comparison is made of shielding requirements for radiation generated by several materials commonly used in neutron optical elements and beam stops, including lithium-6 based absorbers where the Monte Carlo method can model the effects of fast neutrons generated by this material. Crown copyright © 2006 Published by Elsevier B.V.
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    Radiation shielding design for neutron diffractometers assisted by Monte Carlo methods
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Ersez, T; Braoudakis, G; Osborn, JC
    The absorption and scattering of neutrons by neutron optical elements, beam stops and other components present significant radiation shielding challenges due to the generation of gamma radiation. In the case of neutron absorbers incorporating lithium- 6, fast neutrons are also generated. We show how Monte Carlo simulations using the MCNP computer code may be used to model the radiation fields produced by such components, thereby assisting in the choice of materials for shutters and other elements and assisting in the design of shielding. We discuss the use of these techniques to model instrument shielding bunkers, comprised principally of lead walls with boron-containing linings, for diffractometers at the OPAL Reactor, ANSTO. © 2005 The Authors
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    Radiation shielding for neutron guides
    (Elsevier B. V., 2006-11-15) Ersez, T; Braoudakis, G; Osborn, JC
    Models of the neutron guide shielding for the out of bunker guides on the thermal and cold neutron beam lines of the OPAL Reactor (ANSTO) were constructed using the Monte Carlo code MCNP 4B. The neutrons that were not reflected inside the guides but were absorbed by the supermirror (SM) layers were noted to be a significant source of gammas. Gammas also arise from neutrons absorbed by the B, Si, Na and K contained in the glass. The proposed shielding design has produced compact shielding assemblies. These arrangements are consistent with safety requirements, floor load limits, and cost constraints. To verify the design a prototype was assembled consisting of 120 mm thick Pb(96%)Sb(4%) walls resting on a concrete block. There was good agreement between experimental measurements and calculated dose rates for bulk shield regions. Crown Copyright © 2006 Published by Elsevier B.V.
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    Radiation shielding for neutron guides
    (The Institution of Engineers Australia, 2005-11-27) Ersez, T; Braoudakis, G; Osborn, JC
    Models of the neutron guide shielding for the out of bunker guides on the thermal and cold neutron beam lines of the OPAL Reactor (ANSTO) were constructed using the Monte Carlo code MCNP 4B. The neutrons that were not reflected inside the guides but were absorbed by the supermirror (SM) layers were noted to be a significant source of gammas. Gammas also arise from neutrons absorbed by the B, Si, Na and K contained in the glass. The proposed shielding design has produced compact shielding assemblies. These arrangements are consistent with safety requirements, floor load limits, and cost constraints. To verify the design a prototype was assembled consisting of 120mm thick Pb(96%)Sb(4%) walls resting on a concrete block. There was good agreement between experimental measurements and calculated dose rates for bulk shield regions. © The Authors
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    Small angle and inelastic scattering investigation of nanodiamonds
    (International Conference on Neutron Scattering, 2017-07-12) Osborn, JC; Ersez, T; Lu, W
    Nanodiamond material (~5 nm diameter diamond particles) has the potential to be used in the design of the next generation of cold neutron sources (CNS). It is hoped that a blanket layer of this material surrounding the CNS moderator vessel will reflect very cold neutrons back into the moderator, thus reducing leakage through the vessel wall. In this work nanodiamonds produced by two different techniques have been studied, namely those prepared by the detonation method and by laser ablation of a carbon-hydrocarbon mixture. The analysis of experimental data from USANS, SANS and SAXS measurements performed at Australia’s OPAL reactor suggests that large scale structure such as clustering or aggregation of nanodiamond particles may be determining the scattering. The generalised density of states (GDOS) obtained at 20 K from TOF inelastic neutron scattering measurements showed no low energy states. The GDOS of heated and unheated samples at 300 K are consistent with the proposition that thermal treatment of nanodiamond samples eliminates hydrogen in the form of water absorbed on the nanoparticle surface. Hydrogen bonded to carbon is difficult to remove by thermal treatment.